This invention relates to the field of heavy duty continuous flow material processing equipment, more particularly continuous co-flow combination dryers/grinders for reducing the moisture content of wet, slurry and/or similar materials such as clay. As used herein the materials may include a relatively high liquid-to-solid ratio. Most often the liquid is water. The processing equipment additionally grinds and refines the materials to be processed, separating impurities from materials into usable components.
It is to be understood that the term “co-flow” refers to a design in which the air and material flow in the same direction in the dryer, in contrast to “counter-flow” designs, for example.
In the past, co-flow dryers were capable of drying slurries up to only about 60% moisture in a single pass without adding dry powder to the material to be dried.
Known dryers may include rotary drum dryers and fluidized bed dryers which are typical of other continuous drying processes in which very little mixing action occurs. Air swept tubular dryers have been observed to be more efficient than the rotary drum or fluidized bed type processes. In at least one embodiment, the dryer/grinder 402 is capable of removing 750 pounds of water for every 1000 CFM of air used in the process, at production rates of up to 50 tons per hour of material processed, with a retention time in the dryer in the range of approximately ¼ to 1 minute.
Applicant in the past has contemplated the use of Applicant's dryer as disclosed in U.S. Pat. No. 5,570,517 in the processing/drying of clay and other materials. Applicant recently attempted to process and to dry clay and other materials with applicant's dryer, whereupon applicant discovered that operational modifications were required to successfully accomplish the desired results. Applicant's invention herein is directed to the operational modifications/improvements. Applicant incorporates by reference herein, in their entireties, applicant's co-owned U.S. Pat. Nos. 5,570,517; 5,887,808; 6,248,156; and 6,713,112.
Applicant claims priority to U.S. Provisional Patent Application Ser. No. 61/299,788, filed Jan. 29, 2010, the entire contents of which are incorporated by reference herein in its entirety.
Grinding and comminuting apparatus are used for reducing the size of materials such as food products, chemicals, rubbers, resins, garbage (food waste), waste-paper, wood chips, waste fiber (cloth, gypsum), plastics, glass, metal chips or the like. Conventional grinding/comminuting apparatus such as that disclosed in U.S. Pat. No. 4,129,260, issued Dec. 12, 1978 to Baker, entitled Garbage Disposal, and U.S. Pat. No. 3,973,735, issued Aug. 10, 1976 to Ito et al., entitled Apparatus For Pulverizing And Sorting Municipal Waste, typically include a grinding chamber with high speed rotating beaters/hammers that tear, shred, slash, cut and grind one or more desired products to a desired size as the product(s) are forced between the rotating beaters/hammers, and a set of breaker bars, and to a very limited extent, also between the rotating beaters/hammers, and one or more screening elements.
The dryer/grinder invention also relates to a process and apparatus that facilitates efficient recovery of particulate and/or dust which becomes airborne as a result of a product being exposed to industrial refining and drying processes. Devices have been used in conjunction in an attempt to remove particulate content from the air stream in a controlled manner. Devices such as a conventional centrifuge or cyclone, bag houses and other types of separators have been employed using a number of configurations and methods. A separator may be beneficial, which has the capability to efficiently and effectively capture particulate and/or dust that is picked up in the air stream of current dryer/grinding apparatus.
Materials to be processed may have a particle size of less than approximately one-sixteenth inch and rarely having a size in excess of approximately an inch. Materials may be naturally forming or be waste residue. Materials to be processed may have a large range of moisture content and particle size.
The present invention is directed to a dry process which minimizes the environmental impact associated with the water separation techniques used when processing materials. The present invention captures sand, crushed gravel, silica, sulfur, attapugite clay, bentonite clay, kaolin clay, and calcium and other materials for use in other industries such as the cement and concrete industries. The present invention avoids the initial placement of waste materials in the form of a slurry into the environment, as well as being used to reclaim previous coal slurry impounds. The present invention in addition avoids the use of chemicals during the reclaiming or residual material recovery processes.
In the past materials to be processed may have an undesirable moisture content, requiring the material to be dried by exposing the wet material to heat. The drying of the materials to be processed in this manner may be energy inefficient and costly. The present invention reduces the moisture content of the materials to be processed to a desired level by the introduction of a combination of heat and blown air during the refining process, as opposed to exposure to heat alone. The present invention improves the efficiency of the drying of the materials at a lower and more economical energy consumption level, in order to maximize energy and economic savings. The present invention is ecologically friendly by recovering and converting previously discarded waste into useful value-added products while simultaneously cleansing previously polluted environments.